JP3321040B2 - Open pipe edge preheating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preheating an edge portion of an open pipe, and more particularly, to obtain a welded steel pipe by inductively heating both edges of the open pipe to a temperature range in which joining can be performed and abutting and pressing with a squeeze roll. The present invention relates to an open pipe edge preheating apparatus suitable for use in a method for manufacturing a welded steel pipe.

[0002]

2. Description of the Related Art A welded steel pipe is formed by forming a steel plate or a steel strip (strip steel) into a tube and welding the joint thereof, and is manufactured by various manufacturing methods from a small diameter to a large diameter. Examples include electric resistance welding (electric resistance welding), forge welding, and electric arc welding. For small to medium diameter steel pipes, an electric resistance welding method (electric resistance welded steel pipe, electric resistance welded pipe) utilizing high frequency induction heating is mainly used. This method
Continuously supply the steel strip, form it into a tube with a forming roll to form a tube, and then heat both ends of the open tube to the melting point of the steel by high-frequency induction heating, and then use a squeeze roll to cut both ends. This is a method for producing steel pipes by impact welding of the end faces (for example, the 3rd edition Iron and Steel Handbook, Volume III (2)
1056-1092).

In the above-described method of manufacturing an electric resistance welded tube utilizing high frequency induction heating, since the end surfaces of both edges of the open tube are heated to the melting point of the steel or higher, the molten steel flows under the influence of electromagnetic force, and the generated oxidation occurs. An object is caught in the abutment weld and welding defects such as penetrators or molten steel scatter (flash)
There is a problem that is easy to occur. For this issue,
For example, Japanese Patent Application Laid-Open No. 2-299782 proposes a method for manufacturing an electric resistance welded steel pipe having two heating devices. That is,
The first heating device heats the temperature of both edges of the open tube above the Curie point, the second heating device further heats it above its melting point, and squeezes the two edges with a squeeze roll provided immediately downstream. To produce steel pipes. In addition, JP-A-2-29983
In the publication, a current having a frequency of 45 to 250 kHz is passed by a first heating device, and both edges are preheated. The second heating device is further heated to a temperature equal to or higher than the melting point, and both edges are abutted and pressed by a squeeze roll. An electric resistance welded pipe manufacturing apparatus for manufacturing a steel pipe has been proposed.

[0004] As shown in FIG.
A first work coil 52 and a second work coil 62 are provided in this order from the upstream side on the entry side of the squeeze roll 3, and a first heating power supply 51 and a second heating power supply 61 are respectively connected to the first work coil 52 and the second work coil 62. A heating device 5 and a second heating device 6 are provided, and an impeder 20 made of a ferrite core or silicon steel for increasing a heating effect and improving welding efficiency is inserted into the open pipe 1. 1E is an edge portion.

[0005]

However, in the conventional electric resistance welded pipe manufacturing apparatus, since the preheating is performed by an induction type,
In addition to the poor preheating efficiency, there is a problem that it is necessary to have an induction coil of a different size for each outer diameter of the steel pipe in order to maintain the accuracy of the preheating attained temperature, resulting in a large maintenance load.

Accordingly, the present invention provides a direct-current-type open pipe edge preheating suitable for preheating both edges of an open pipe which is abutted and pressed by a squeeze roll at the entrance of the squeeze roll prior to induction heating. An object of the present invention is to provide an apparatus for improving heating efficiency and reducing maintenance load in the production of welded steel pipes.

[0007]

According to a first aspect of the present invention, there is provided an air conditioner in which both edges of an open pipe abutted and pressed by a squeeze roll are heated before induction heating at the squeeze roll entry side. An open pipe edge portion preheating device for preheating, a power supply roll facing each other across a slit between both edge portions and rollingly contacting each edge portion, and a predetermined distance from a pair of the power supply roll. An open tube edge preheating device, comprising: a conductive bridge roll that rolls and comes into contact with both edges across a slit; and a high-frequency voltage application unit that applies a high-frequency voltage to the pair of power supply rolls. It is.

The present invention described in claim 2 (second invention) provides:
An open pipe edge preheating device for preheating both edges of an open pipe which is abutted and pressed by a squeeze roll before induction heating at an entrance of the squeeze roll. And a high-frequency voltage applying means for applying a high-frequency voltage of opposite phase to a pair of power supply rolls facing each other at the same position. This is the open pipe edge preheating device that is the feature.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1A and 1B show a first embodiment of the present invention, and FIG. 1B is a schematic diagram showing an entire circuit, and FIG. 1B is a circuit diagram suitable for high-frequency voltage applying means. In FIG. 1, 1 is an open tube, 1
E is an edge portion, 1S is a slit, 2 is an induction heating device, 2
A is a high frequency heating power supply, 2B is a work coil, 3 is a squeeze roll, 4 is a steel pipe, 7 is a power supply roll, 8 is a bridge roll, 9 is a high frequency voltage applying means, 10 is a high frequency preheating power supply,
11 is a tank capacitor, and 12 is a current transformer.

In the first invention, as shown in FIG. 1, both edges 1E of an open pipe 1 which is abutted and pressed by a squeeze roll 3 are connected to the squeeze roll 3 entry side by, for example, a high-frequency heating power supply 2A and a high-frequency heating power supply 2A. An open-tube edge preheating device for preheating before induction heating by an induction heating device 2 including a work coil 2B to be connected. The open tube edge portion preheating device opposes a slit 1S between both edge portions 1E and is turned to each edge portion 1E. A power supply roll 7 (7a, 7b) movably contacting, and a conductive bridge roll 8 rotatably contacting both edge portions 1E across a slit 1S at a predetermined distance from a pair of the power supply rolls 7 And a high-frequency voltage applying means 9 for applying a high-frequency voltage to a pair of the power supply rolls 7. Note that the positions of the pair of power supply rolls 7 and the bridge roll 8 may be interchanged.

With this configuration, the high-frequency current is applied to the high-frequency voltage applying means 9, the power supply roll 7a, one edge portion 1E, the bridge roll 8,
The other edge portion 1E to the power supply roll 7b to the high-frequency voltage applying means 9 flow along the path, and the opposite edge portions 1E on both sides of the slit 1S are opposite to each other (the direction shown by the arrow, and the solid line and the broken line are alternated). ), The current is further concentrated on this portion by the proximity effect.

FIGS. 2A and 2B illustrate the second invention, and FIG. 2A is a schematic diagram, and FIGS. 2B and 2C are circuit diagrams suitable for high-frequency voltage applying means. 2, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the second invention, as shown in FIG. 2, both edges 1E of the open pipe 1 abutted and pressed by the squeeze roll 3 are connected to the squeeze roll 3 on the inlet side, for example, with a high-frequency heating power supply 2A and a work connected to the same. By the induction heating device 2 composed of the coil 2B,
An open-tube edge preheating device for preheating before induction heating, which faces two edges at a predetermined distance across a slit 1S between both edge portions 1E and comes into rolling contact with each edge portion 1E. Power supply roll 7 (7a, 7b, 7
c, 7d) and high-frequency voltage applying means 9 for applying high-frequency voltages having opposite phases to a pair ((7a, 7b) and (7c, 7d)) of the power supply rolls 7 facing each other at the same position. This is the open pipe edge preheating device that is the feature.

With this configuration, the high-frequency current is supplied by the high-frequency voltage applying means 9 to the power supply roll 7a to one edge 1E to the power supply roll 7c to the power supply roll 7b to the other edge 1E to the power supply roll by the skin effect and the edge effect. 7d ~
High-frequency voltage applying means 9 flows along a path, and currents flow in opposite directions (directions indicated by arrows, solid lines and dashed lines are alternating) in edge portions 1E opposed to each other on both sides of slit 1S. As in the invention, the current is further concentrated on this part by the proximity effect.

According to the first aspect, the edge portion 1E to which the high-frequency current is opposed via the pair of power supply rolls 7 and the bridge roll 8, and according to the second aspect of the invention via the two pairs of power supply rolls 7. Since the current is directly supplied to the open pipe 1, an eddy current is not wastefully generated in the peripheral portion of the pipe other than the edge of the open pipe 1 as in the induction type, so that the preheating efficiency is improved. For example, according to the first and second aspects of the present invention, an open pipe edge having an outer diameter of 88 mm, a wall thickness of 3 mm, and a material passing speed of 70 m / min is heated to a heating width (a range of an edge portion to reach a target temperature; (Indicated by the length along the circumferential direction from the end face to the inside of the pipe)
When preheating up to 900 ° C or more with 3 mm = 3 mm, the electric power is about 90% or less of the induction type.

[0015] Further, since the apparatus is configured such that rotary electric current (a pair of power supply rolls 7 and a bridge roll 8 or two pairs of power supply rolls 7) is brought into contact with the edge portion 1E to directly energize, the outer diameter of the open tube 1 is increased. Can be dealt with by a simple arrangement change such as adjusting the interval between the power supply rolls 7 sandwiching the slit 1S, so that the maintenance load is reduced. In addition, since the rotating electronic members are in rolling contact with the open tube 1 in the passage, the friction is small, and the open tube 1 does not generate scratches.

[0016] As a material of the rotating electron, high conductivity,
A W alloy (for example, an Ag-W alloy, a Cu-W alloy, etc.) having abrasion resistance is preferable. The preheating section (the distance between the feeding roll pair and the bridge roll in the material passing direction or the distance between the feeding roll pairs) is preferably sufficiently shorter than the circumferential length of the open pipe 1, for example, about the outer diameter of the open pipe 1. Is used as a rough guide.

Although not shown, the configuration of the support member for rotatably fixing the rotating electron beam to a desired position can be freely selected in consideration of the engagement with other surrounding members. Needless to say, such supporting members need to be electrically insulated from the rotating electrons to be supported by them. The frequency of the high-frequency preheating power supply 10 is several tens according to the heating width.
It is preferable to appropriately select from the range of kHz to several hundred kHz.

In particular, in the case of a small-diameter open tube, the distance in the circumferential direction of the tube is shortened, the electric resistance is reduced, and the current easily escapes in the circumferential direction of the tube. Thus, it is desirable to prevent such escape of the current. Also, t / D (t: pipe wall thickness,
(D: outer diameter of the pipe) is small and there is a concern that the open pipe edge may be deformed by the pressing force for contacting the power supply roll, as shown in FIG. 13 is preferably arranged. In FIG. 3, reference numeral 14 denotes a support roll support frame.

[0019]

As described above, according to the present invention, it is possible to employ an electric heating method when preheating the both edges of the open pipe to be abutted and pressed by the squeeze roll before induction heating at the squeeze roll entry side. This has the effect of improving the preheating efficiency.

[Brief description of the drawings]

FIG. 1 (a) exemplifies a first invention;
(B) is a circuit diagram suitable for the high-frequency voltage applying means.

FIG. 2A is an overall schematic view illustrating the second invention,
(B), (c) is a circuit diagram suitable for high-frequency voltage application means.

FIG. 3 is an explanatory diagram of a mode in which a pressing force of a power supply roll is received by a support roll.

FIG. 4 is a schematic view of a conventional ERW pipe manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Open pipe 1E Edge part 1S slit 2 Induction heating device 2A High frequency heating power supply 2B Work coil 3 Squeeze roll 4 Steel pipe 5 First heating device 6 Second heating device 7 Feeding roll 8 Bridge roll 9 High frequency voltage applying means 10 High frequency preheating Power supply 11 Tank capacitor 12 Current transformer 13 Support roll 14 Support roll support frame 20 Impeder 51 First heating power supply 52 First work coil 61 Second heating power supply 62 Second work coil

Continuation of the front page (72) Inventor Toshio Onishi 1-1-1, Kawasaki-cho, Handa-shi, Aichi Prefecture Kawasaki Steel Corporation Chita Works (72) Inventor Nobuki Tanaka 1-1-1, Kawasaki-cho, Handa-shi, Aichi Prefecture Kawasaki Steel Corporation Chita Corporation Inside the factory (72) Masaro Shoji Inventor 1-1, Kawasaki-cho, Handa-shi, Aichi Prefecture Inside the Chita Works, Kawasaki Steel Corporation (56) References JP-A-9-1366 (JP, A) JP-A 7-1170 (JP) , A) JP-A-8-33989 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 13/00 B21C 37/08 B23K 26/00 H05B 3/00

Claims (2)

(57) [Claims] 1. An open pipe edge preheating device for preheating both edges of an open pipe abutted and pressed by a squeeze roll before induction heating at an inlet side of the squeeze roll, wherein a slit between the two edges is formed. A power supply roll that sandwiches and opposes each other so as to be in rolling contact with each edge portion, and a conductive bridge roll that is rotatably contacted with both edge portions across a slit at a predetermined distance from the pair of power feeding rolls When,
And a high-frequency voltage applying means for applying a high-frequency voltage to the pair of power supply rolls. 2. An open pipe edge preheating apparatus for preheating both edges of an open pipe which is abutted and pressed by a squeeze roll before induction heating at an entrance side of the squeeze roll, comprising two positions at a predetermined distance. And a high-frequency voltage applying means for applying high-frequency voltages of opposite phases to a pair of power supply rolls facing each other with the slit between the two edge portions and being in rolling contact with each edge portion, and a pair of power supply rolls facing each other at the same position. An open pipe edge portion preheating device, comprising: